Ground handoff map values through explicit canonical fact bindings

tests/test_compact_handoff.py

@@ -100,6 +100,11 @@ def test_existing_v2_call_stays_frozen_after_upgrade(diagnosed):
     store, _ = diagnosed
     adapter = RequestAdapter()
     builder = ChangeRequestBuilder(store, gateway(adapter))
+    original_context = builder.context
+    def legacy_context(reader, policy, **kwargs):
+        kwargs['parameter_grounding'] = 1
+        return original_context(reader, policy, **kwargs)
+    builder.context = legacy_context
     original = builder._request
     builder._request = lambda reader, context, operation, **kw: original(
         reader, context, operation, version='change_request_v2')
@@ -108,6 +113,7 @@ def test_existing_v2_call_stays_frozen_after_upgrade(diagnosed):
     with pytest.raises(ChangeRequestError):
         build(builder)
     builder._request = original
+    builder.context = original_context
     builder.publish = publish
     assert build(builder).status == 'COMPLETED'
     assert build(builder).reused and adapter.calls == 1